China’s two-time grand slam winner Li Na is set to announce her retirement, according to widespread reports in her home country.

China’s state broadcaster CCTV claims the world No6 Li, who won the 2011 French Open and 2014 Australian Open singles titles, has chosen to hang up her raket due to knee injury concerns.

CCTV cites unnamed sources as saying the announcement will come on Friday. Li, 32, has not commented on the reports.

CCTV said on its micro-blogging site: “According to insiders who broke the news, Li Na, who won two women’s tennis grand slams, will officially announce her retirement publicly tomorrow.”

Li’s last message on Chinese social media website Weibo was sent on 5 September, saying: “I love this job and am delighted for your encouragement, my career is the fight of my life, your encouragement is my greatest happiness.”

The world number six has not played since losing in the third round at Wimbledon in June to Czech player Barbora Zahlavova Strycova, sitting out the US Open.

At Wimbledon, she said that prior to the tournament she had taken a “vacation to think about what I should do in the future”.

Organisers of next week’s Wuhan Open, the tournament held in her home city of Wuhan, still have Li on their competitors’ list.

Li’s success in becoming Asia’s first grand slam singles champion has made her a national sporting hero in China, with Time Magazine naming her among its 100 most influential people in the world in 2013, and featuring her as the cover star.

Her off-court earnings have been vast, outweighing on-court income, with Li behind only Maria Sharapova in this year’s Forbes list of highest-paid female athletes. She was estimated to have earned around £14.5m in total for the 12 months to June 2014.